In recent years, a memory card has been well accepted in the market as a semiconductor memory media having a large storage capacity. The memory card is widely used in portable digital devices such as digital cameras, portable music players, and portable information terminals. In order to use the memory card in the broader range of fields, the memory card has been required to have a wireless communication function.
An SD memory card with a wireless interface function is disclosed in, e.g. patent document 1 as a product satisfying the foregoing requirement. This SD memory card disclosed in patent document 1 is described hereinafter with reference to FIG. 15 and FIG. 16. FIG. 15 shows a schematic diagram illustrating a structure of the memory card disclosed in patent document 1, and FIG. 16 shows a perspective view illustrating an appearance of the SD memory card.
As shown in FIG. 15 and FIG. 16, SD memory card 1410 includes wireless controller 1430 besides the main function of memory medium, and antenna module 1420 equipped with antenna 1450 is coupled to wireless controller 1430 via connector 1440. Flash memory 1460 works as a flash ROM for the memory of SD memory card 1410 and also stores a driver program for operating the wireless communication function.
An electronic device, such as a portable digital device, equipped with SD card 1410 coupled to antenna module 1420 is capable of communicating with an external wireless communicating device without any special operation. In patent document 1 discussed above discloses that antenna module 1420 is retrofitted to an end of SD memory card 1410. Another example is also disclosed: antenna 1450 is built in SD memory card 1410 along the end face opposite to another end face where an external connecting terminal is disposed so that the housing of SD memory card can be free from any protrusions therefrom.
On the other hand, an electronic circuit module including multiple circuit boards is downsized by covering a first face of each one of the multiple boards with one sheet of a double-sided flexible circuit board so that each one of the multiple circuit boards can be coupled together mechanically and electrically. This technique is disclosed in, e.g. patent document 2. Since the double-sided flexible circuit board can be bent, the foregoing structure allows layering or folding the multiple circuit boards.
SD memory card 1410 disclosed in patent document 1; however, is retrofitted with antenna module 1420 at its end, so that its outer dimensions become greater by the size of antenna module 1420. In order to solve this problem, another example is disclosed: the SD memory card is equipped with an antenna built therein along its end face opposite to another end face where an external connecting terminal is disposed. This structure can work at 2.4 GHz band which is specified in the example; however, in the case of using 13.56 MHz band, a longer antenna is needed, so that it is difficult to place the antenna along the end face.
According to patent document 2, use of the double-sided flexible circuit board for covering a first face of each one of the multiple circuit boards allows coupling the multiple circuit boards together electrically and mechanically; however, patent document 2 is not disclosed about a wireless function such as an antenna, or problems of degrading the wireless function as well as measures to overcome the problems.
Patent document 1: Unexamined Japanese Patent Publication No. 2001-195553
Patent document 2: Unexamined Japanese Patent Publication No. H04-233786